Double-sided shear tester for shear strength of root soil and experimental method

Abstract

The invention belongs to the technical field of rock-soil and ecological engineering experiments, and particularly relates to a double-sided shear tester for the shear strength of root soil and an experimental method. The sample shearing mechanism is used for placing a sample obtained by in-situ culture of a target soil body; the sample shearing mechanism is arranged in the middle of the main body frame; the sample shearing mechanism comprises a lower fixing ring and an upper fixing ring which are fixed with the main body frame, and a shearing ring which is in horizontal sliding fit with the main body frame, the shearing ring is positioned between the lower fixing ring and the upper fixing ring, the lower fixing ring and the upper fixing ring are coaxially arranged, and when the shearing ring and the lower fixing ring are coaxial, the shearing ring and the upper fixing ring are coaxially arranged. The inner sides of the lower fixing ring, the shearing ring and the upper fixing ring form a cavity for placing a sample; a counter-force unit is arranged in the lower fixing ring, and a pressurizing unit is arranged in the upper fixing ring; one side of the shearing ring is in transmission fit with the movable end of the telescopic mechanism, and a sensor is arranged on the shearing ring; the moving direction of the shearing ring is parallel to the radial direction of the lower fixing ring. The invention further discloses a testing method using the device.

Description

Technical Field

[0001] This invention belongs to the field of experimental technology of geotechnical and ecological engineering, and particularly relates to a double-sided shear strength tester and experimental method for root soil. Background Technology

[0002] Root reinforcement is one of the core mechanisms for ecological slope protection and soil erosion control. Quantitatively obtaining the shear strength parameters of the root-soil composite is crucial for slope stability calculations and ecological restoration design. Currently, the main technical methods for obtaining the shear strength of root soil fall into two categories: indoor direct shear tests and large-scale in-situ shear tests.

[0003] Indoor direct shear testing is currently the most commonly used method. The standard procedure is as follows: First, plants are grown in pots in a greenhouse or laboratory to cultivate root-soil complexes; or undisturbed soil samples are collected from the field. Then, the potted soil or undisturbed soil samples are prepared into standard-sized direct shear specimens through pressing and trimming. Finally, the shear test is performed on a direct shear apparatus. While this method allows for control of experimental conditions, it has inherent drawbacks such as poor ecological realism, significant sampling disturbance, and poor sample comparability. Furthermore, because indoor direct shear equipment only has one shear plane, stress concentration can affect the experimental data.

[0004] In addition, outdoor in-situ testing methods are difficult to promote due to their high cost and complex equipment.

[0005] Currently, there is a lack of a root soil shear strength testing technology and device that can balance ecological accuracy with laboratory testing precision, while also offering advantages such as low cost, ease of operation, and repeatability. Therefore, there is an urgent need for a root soil shear strength double-sided shear tester and experimental method to address this issue. Summary of the Invention

[0006] The purpose of this invention is to provide a double-sided shear strength tester and experimental method for root soil to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A two-sided shear strength tester for root soil includes:

[0009] Main framework;

[0010] A sample shearing mechanism is used to place a sample obtained from in-situ culture of target soil. The sample shearing mechanism is located in the middle of the main frame. The sample shearing mechanism includes a lower fixing ring and an upper fixing ring fixed to the main frame, and a shearing ring that slides horizontally with the main frame. The shearing ring is located between the lower fixing ring and the upper fixing ring. The lower fixing ring and the upper fixing ring are coaxially arranged. When the shearing ring is coaxial with the lower fixing ring, the inner sides of the lower fixing ring, the shearing ring, and the upper fixing ring form a cavity for placing the sample.

[0011] A reaction force unit is provided inside the lower fixing ring, and a pressurizing unit is provided inside the upper fixing ring;

[0012] One side of the shear ring is driven to the movable end of the telescopic mechanism, and a sensor is provided on the shear ring;

[0013] The direction of movement of the shearing ring is parallel to the radial direction of the lower fixed ring.

[0014] Optionally, a slidable base is fixedly connected to the bottom of the shearing ring. The slidable base includes a fixing block and a slider. The slider is fixed to the shearing ring, and the fixing block is fixed to the main frame.

[0015] Optionally, the reaction unit includes a lower pressure cover, which is coaxially disposed inside the lower fixing ring. One end of the lower pressure cover is fixedly connected to a left fixing nut, and the other end of the left fixing nut is fixedly connected to the main frame.

[0016] The lower pressure cap is in contact with one end of the sample.

[0017] Optionally, the pressurization unit includes:

[0018] An upper pressure cap is coaxially disposed within the upper fixing ring, and the upper pressure cap is slidably engaged with the upper fixing ring;

[0019] The force transmission lever has one end fixedly connected to the upper pressure cover, the middle part of the force transmission lever is slidably fitted to the side wall of the main frame, and the other end of the force transmission lever is in contact with the middle part of the lever.

[0020] One end of the lever is hinged to the side wall of the main frame, and the other end of the lever is connected to a force-applying part.

[0021] Optionally, the force-applying part includes:

[0022] A pulley is rotatably mounted on the main frame; a rope is wound around the pulley, one end of the rope is fixed to one end of the lever, and the other end of the rope is fixed to the top of a pressure rod. A tray is fixed to the bottom end of the pressure rod, and a weight is placed on the tray.

[0023] Optionally, the telescopic mechanism includes:

[0024] The telescopic rod is slidably engaged with the main frame, and one end of the telescopic rod contacts one side of the shear ring;

[0025] The drive unit is in transmission cooperation with the telescopic rod.

[0026] Optionally, the drive unit includes a stepper motor, the output shaft of which is shaft-connected to a worm gear, the worm gear meshing with a turbine, the turbine having internal threads, the turbine being sleeved on the outside of the telescopic rod, and the telescopic rod engaging with the turbine threadedly;

[0027] The telescopic rod is provided with a sliding groove, and the main frame is provided with a protrusion. The telescopic rod and the main frame are axially sliding and radially limited through the cooperation of the sliding groove and the protrusion.

[0028] Optionally, the sensor includes a load sensor and a shear displacement sensor, the load sensor and the shear displacement sensor being located on opposite sides of the shear ring, respectively;

[0029] One end of the load sensor is fixedly connected to the telescopic rod, and the other end of the load sensor is in contact with the side wall of the shear ring;

[0030] The fixed end of the shear displacement sensor is fixedly connected to the main frame, and the movable end of the shear displacement sensor is in contact with the side wall of the shear ring.

[0031] The experimental method for the two-sided shear strength test of root soil, using the aforementioned two-sided shear strength tester for root soil, includes the following steps:

[0032] The sample obtained from in-situ culture of the target soil is placed into the cavity formed by the lower fixing ring, the shear ring and the inner side of the upper fixing ring;

[0033] The reaction force unit provides a reaction force to one end of the sample;

[0034] Pressure is applied to the other end of the sample via the pressurizing unit;

[0035] The movable end of the telescopic mechanism extends out and pushes against one side of the shear ring, causing it to move.

[0036] Experimental data is acquired and processed using the sensor.

[0037] Optionally, the method for obtaining the sample through in-situ culture of the target soil includes the following steps:

[0038] A standard cylindrical PVC pipe with a smooth inner wall is buried in the soil of the target site.

[0039] The target plant is planted inside the PVC pipe;

[0040] The target plant is allowed to grow naturally in the soil of the target site under in-situ stress, moisture and ecological environment for a predetermined period of time;

[0041] After growth is complete, the PVC pipe, together with the complete root-soil composite formed inside the pipe, is excavated from the site as a whole sample and transported back to the laboratory.

[0042] Compared with the prior art, the present invention has the following advantages and technical effects:

[0043] In use, the sample obtained from in-situ cultivation of the target soil is placed into the cavity formed by the lower fixed ring, the shear ring, and the inner side of the upper fixed ring. The reaction force unit provides a reaction force to one end of the sample, and the pressurization unit provides pressure to the other end of the sample. At this time, the movable end of the telescopic mechanism extends and presses against one side of the shear ring, causing it to move. Displacement and thrust data are acquired by sensors. By placing the shear ring between the upper and lower fixed rings, two shear surfaces are formed on the sample when the shear ring moves. Compared with the traditional single shear surface, stress concentration at the shear surface can be avoided, thus avoiding the influence of stress on the experimental data. At the same time, the sample is obtained from in-situ cultivation of the target soil, which can achieve the accuracy of in-situ test data and avoid the defects of high cost and complex equipment in in-situ tests. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a top view of the structure of the present invention;

[0046] Figure 2 This is a left view of the structure at the shear ring of the present invention;

[0047] Figure 3 This is a left view of the structure at the upper or lower fixing ring of the present invention;

[0048] The components include: 1. Stepper motor; 2. Load sensor; 3. Lever; 4. Force transmission lever; 5. Pulley; 6. Pressure rod; 7. Weight; 8. Tray; 9. Upper pressure cover; 10. Upper fixing ring; 11. Shearing ring; 12. Lower fixing ring; 13. Lower pressure cover; 14. Left side fixing nut; 15. Fixing bolt; 16. Sliding base; 17. Base; 18. Main frame; 19. Shear displacement sensor; 20. Fixed base. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Reference Figures 1 to 3 This invention discloses a double-sided shear strength tester for root soil, comprising:

[0052] Main framework 18;

[0053] The sample shearing mechanism is used to place the sample obtained by in-situ cultivation of the target soil. The sample shearing mechanism is located in the middle of the main frame 18. The sample shearing mechanism includes a lower fixing ring 12 and an upper fixing ring 10 fixed to the main frame 18, and a shearing ring 11 that is horizontally slidably engaged with the main frame 18. The shearing ring 11 is located between the lower fixing ring 12 and the upper fixing ring 10. The lower fixing ring 12 and the upper fixing ring 10 are coaxially arranged. When the shearing ring 11 is coaxial with the lower fixing ring 12, the inner sides of the lower fixing ring 12, the shearing ring 11 and the upper fixing ring 10 form a cavity for placing the sample.

[0054] A reaction unit is installed inside the lower fixed ring 12, and a pressurizing unit is installed inside the upper fixed ring 10;

[0055] One side of the shear ring 11 is driven to the movable end of the telescopic mechanism, and a sensor is provided on the shear ring 11;

[0056] The direction of movement of the shear ring 11 is parallel to the radial direction of the lower fixed ring 12.

[0057] In use, the sample obtained from in-situ cultivation of the target soil is placed into the cavity formed by the lower fixed ring 12, the shear ring 11, and the upper fixed ring 10. The reaction force unit provides a reaction force to one end of the sample, and the pressurization unit provides pressure to the other end of the sample. At this time, the movable end of the telescopic mechanism extends and pushes against one side of the shear ring 11, causing it to move. Displacement and thrust data are acquired by sensors. By placing the shear ring 11 between the upper fixed ring 10 and the lower fixed ring 12, two shear surfaces are formed on the sample when the shear ring 11 moves. Compared with the traditional single shear surface, stress concentration at the shear surface can be avoided, thus avoiding the influence of stress on the experimental data. At the same time, the sample is obtained from in-situ cultivation of the target soil, which can achieve the accuracy of in-situ test data and avoid the defects of high cost and complex equipment in in-situ tests.

[0058] The upper fixing ring 10 and the lower fixing ring 12 are fixed to the main frame 18 by fixing bolts 15.

[0059] The shear ring 11, upper fixed ring 10, and lower fixed ring 12 are joined together to form a cylinder with their axis placed horizontally. During the test, the upper fixed ring 10 and lower fixed ring 12 on both sides are fixed and provide horizontal reaction force, while the shear ring 11 forms a double shear surface through translation. Guide rails are provided on the sides to limit its rotation, thereby ensuring stability in the shear direction.

[0060] Furthermore, the inner diameter of the shear ring 11, the upper fixing ring 10, and the lower fixing ring 12 are all 10cm, and the wall thickness is 1cm.

[0061] Both the upper fixing ring 10 and the lower fixing ring 12 are fixedly connected to a fixing base 20 at their bottoms. The fixing base 20 is fixedly connected to a base 17 at its bottom, and the base 17 is fixed to the main frame 18.

[0062] As an optional implementation, a slidable base 16 is fixedly connected to the bottom of the shear ring 11. The slidable base 16 includes a fixing block and a slider. The slider is fixed to the shear ring 11, and the fixing block is fixed to the main frame 18.

[0063] The base 17 is equipped with a slide rail, and the fixed base 20 is equipped with a slide groove. Through the cooperation of the slide rail and the slide groove, the shearing ring 11 and the main frame 18 can slide horizontally.

[0064] As an optional implementation, the reaction unit includes a lower pressure cover 13, which is coaxially disposed inside the lower fixing ring 12. One end of the lower pressure cover 13 is fixedly connected to a left fixing nut 14, and the other end of the left fixing nut 14 is fixedly connected to the main frame 18.

[0065] The lower pressure cap 13 contacts one end of the sample.

[0066] The lower pressure cover 13, which is provided inside the lower fixing ring 12, is fixed to the main frame 18 by the left fixing nut 14, and is used to provide a reaction force when pressure is applied to the sample.

[0067] As an optional implementation, the pressurization unit includes:

[0068] The upper pressure cover 9 is coaxially disposed inside the upper fixing ring 10, and the upper pressure cover 9 and the upper fixing ring 10 are in sliding fit.

[0069] The force transmission lever 4 is fixedly connected to the upper pressure cover 9 at one end, and the middle part of the force transmission lever 4 is slidably fitted on the side wall of the main frame 18. The other end of the force transmission lever 4 is in contact with the middle part of the lever 3.

[0070] One end of lever 3 is hinged to the side wall of the main frame 18, and the other end of lever 3 is connected to the force-applying part.

[0071] By applying force to one end of lever 3, the other end of lever 3 is hinged to the side wall of the main frame 18, causing lever 3 to rotate around the hinge point. After the middle part of lever 3 contacts one end of the force transmission lever 4, it squeezes the end of the force transmission lever 4 to make it slide on the side wall of the main frame 18, and drives the upper pressure cover 9 to slide in the upper fixing ring 10, thereby applying pressure to the sample.

[0072] As an optional implementation, the force-applying part includes:

[0073] The pulley 5 is rotatably mounted on the main frame 18; a rope is wound around the pulley 5, one end of the rope is fixed to one end of the lever 3, and the other end of the rope is fixed to the top of the pressure rod 6. The bottom end of the pressure rod 6 is fixed to the tray 8, and a weight 7 is placed on the tray 8.

[0074] The weight 7 causes the tray 8 to descend, pulling the pressure rod 6 and pulling the rope. The other end of the rope moves one end of the lever 3 in the horizontal plane through the pulley 5, thereby applying pressure to the force transmission lever 4. The pressure is then transmitted to the upper pressure cover 9 and applied to the end of the sample through the force transmission lever 4.

[0075] The pressure applied to the sample can be adjusted by changing the weights 7 of different weights 9.

[0076] The weight 7 is applied to the lever 3 by the pulley 5, thereby generating horizontal pressure on the sample.

[0077] As an optional implementation, the telescopic mechanism includes:

[0078] The telescopic rod is slidably fitted with the main frame 18, and one end of the telescopic rod is in contact with one side of the shear ring 11.

[0079] The drive unit works in conjunction with the telescopic rod transmission.

[0080] As an optional implementation, the drive unit includes a stepper motor 1, the output shaft of the stepper motor 1 is shaft-connected to a worm gear, the worm gear meshes with a turbine gear, the turbine gear is provided with a thread, the turbine gear is sleeved on the outside of the telescopic rod, and the telescopic rod and the turbine gear are threaded together.

[0081] The telescopic rod is provided with a sliding groove, and the main frame 18 is provided with a protrusion. The telescopic rod and the main frame 18 achieve axial sliding and radial limiting through the cooperation of the sliding groove and the protrusion.

[0082] The worm gear mechanism allows the telescopic rod to slide horizontally under the action of the thread, thus pushing the shear ring 11 to move.

[0083] As an optional implementation, the sensor includes a load sensor 2 and a shear displacement sensor 19, which are located on both sides of the shear ring 11, respectively.

[0084] One end of the load sensor 2 is fixed to the telescopic rod, and the other end of the load sensor 2 is in contact with the side wall of the shear ring 11;

[0085] The fixed end of the shear displacement sensor 19 is fixedly connected to the main frame 18, and the movable end of the shear displacement sensor 19 is in contact with the side wall of the shear ring 11.

[0086] Load sensor 2 and shear displacement sensor 19 acquire the pressure applied to shear ring 11 and the displacement of shear ring 11, respectively.

[0087] The shear force on the specimen is measured by load sensor 2 and shear displacement sensor 19.

[0088] The experimental method for the two-sided shear strength test of root soil, using the aforementioned two-sided shear strength tester for root soil, includes the following steps:

[0089] The sample obtained from in-situ culture of the target soil is placed into the cavity formed by the inner side of the lower fixing ring 12, the shear ring 11 and the upper fixing ring 10.

[0090] A reaction force is provided to one end of the specimen through a reaction force unit;

[0091] Pressure is applied to the other end of the sample via a pressurizing unit;

[0092] The movable end of the telescopic mechanism extends out and presses against one side of the shear ring 11, causing it to move.

[0093] Experimental data is acquired and processed using sensors.

[0094] As an optional implementation method, the method for obtaining samples through in-situ culture of the target soil includes the following steps:

[0095] A standard cylindrical PVC pipe with a smooth inner wall is buried in the soil of the target site.

[0096] Planting the target plant inside a PVC pipe;

[0097] The target plants are allowed to grow naturally in the soil of the target site under in-situ stress, moisture and ecological environment until the predetermined period is reached;

[0098] After growth was complete, the PVC pipe, along with the complete root-soil composite formed inside the pipe, was excavated from the site as a whole sample and transported back to the laboratory.

[0099] An in-situ simulation method for two-sided shear strength testing of root soil is presented. The specific steps of this method are as follows:

[0100] Step 1: In-situ sample cultivation and retrieval.

[0101] Bury a standard cylindrical PVC pipe with a smooth inner wall (e.g., 10cm in diameter and 20cm in height) into the soil of the target site.

[0102] Plant the target plant (such as alfalfa) in the pipe and let it grow naturally in the in-situ stress, water and ecological environment until the predetermined cycle (such as a growing season).

[0103] After growth was complete, the PVC pipe, along with the intact root-soil complex formed inside, was carefully excavated from the site as a single specimen and transported back to the laboratory. This process ensured the preservation of the original structure of the root-soil complex.

[0104] Step 2: Sample saturation and installation.

[0105] To simulate saturation, the bottom of the sample can be placed in a water tank, and the sample can be slowly saturated from the bottom up through capillary action.

[0106] The PVC pipe containing the specimen is precisely installed in the instrument's retaining ring, ensuring it is vertical and centered. A predetermined normal stress (σ) is applied to the top of the specimen using a pressurization device to simulate overburden pressure at different depths.

[0107] Step 3: Perform a double-sided shear test.

[0108] Set the test parameters: Set the shear rate (e.g., 0.8 mm / min) using the controller.

[0109] Start-up test: The controller drives the shear ring to move, gradually applying shear force to the middle of the sample.

[0110] Synchronous data acquisition: Throughout the entire cutting process, the system automatically records the following data synchronously:

[0111] Real-time shear force (τ) from intermediate load sensor 2.

[0112] Shear displacement (S) recorded by shear displacement sensor 19.

[0113] Step 4: Data calculation and analysis.

[0114] Calculate the total shear force (τ) under a certain pressure level, i.e., the mass of weight 7: Since it is a double-sided symmetrical shear, the total shear force is the ratio of the shear force sensor reading to the area of ​​the two shear surfaces, i.e., τ = F / (2A).

[0115] Where F is the shear force sensor reading and A is the area of ​​the shear surface.

[0116] Calculate shear strength (τ) f ): Plot the relationship curve between shear stress (τ) and shear displacement (S), and take the peak value or stable value of the curve as the shear strength (τ) of the root soil. f ).

[0117] Determine the strength parameters (c, φ): Replace with weights of different masses 7 and repeat the above experiment to obtain at least four sets of (σ, τ) values. f Data. Linear fitting was performed based on the Coulomb strength criterion.

[0118] Formula: τ f = c +σtan(φ)

[0119] The intercept of the fitted straight line is the cohesion c of the root soil.

[0120] The slope of the fitted straight line is the internal friction angle φ of the root soil.

[0121] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0122] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A double-sided shear strength tester for root soil, characterized in that, include: Main framework (18); A sample shearing mechanism is used to place a sample obtained from in-situ culture of the target soil. The sample shearing mechanism is located in the middle of the main frame (18). The sample shearing mechanism includes a lower fixing ring (12) and an upper fixing ring (10) fixed to the main frame (18), and a shearing ring (11) that slides horizontally with the main frame (18). The shearing ring (11) is located between the lower fixing ring (12) and the upper fixing ring (10). The lower fixing ring (12) and the upper fixing ring (10) are coaxially arranged. When the shearing ring (11) is coaxial with the lower fixing ring (12), a cavity for placing the sample is formed on the inner side of the lower fixing ring (12), the shearing ring (11) and the upper fixing ring (10). A reaction force unit is provided inside the lower fixing ring (12), and a pressurizing unit is provided inside the upper fixing ring (10); One side of the shear ring (11) is driven to the movable end of the telescopic mechanism, and a sensor is provided on the shear ring (11); The direction of movement of the shearing ring (11) is parallel to the radial direction of the lower fixed ring (12).

2. The root soil shear strength double-sided shear tester according to claim 1, characterized in that: The bottom of the shearing ring (11) is fixedly connected to a sliding base (16). The sliding base (16) includes a fixing block and a slider. The slider is fixed to the shearing ring (11), and the fixing block is fixed to the main frame (18).

3. The root soil shear strength double-sided shear tester according to claim 1, characterized in that: The reaction unit includes a lower pressure cover (13), which is coaxially arranged inside the lower fixing ring (12). One end of the lower pressure cover (13) is fixedly connected to the left side fixing nut (14), and the other end of the left side fixing nut (14) is fixedly connected to the main frame (18). The lower pressure cap (13) is in contact with one end of the sample.

4. The root soil shear strength double-sided shear tester according to claim 1, characterized in that, The pressurization unit includes: The upper pressure cover (9) is coaxially disposed inside the upper fixing ring (10), and the upper pressure cover (9) and the upper fixing ring (10) are in sliding fit; One end of the force transmission lever (4) is fixed to the upper pressure cover (9), the middle part of the force transmission lever (4) is slidably fitted on the side wall of the main frame (18), and the other end of the force transmission lever (4) is in contact with the middle part of the lever (3). One end of the lever (3) is hinged to the side wall of the main frame (18), and the other end of the lever (3) is connected to a force-applying part.

5. The root soil shear strength double-sided shear tester according to claim 4, characterized in that, The force-applying part includes: A pulley (5) is rotatably mounted on the main frame (18); a rope is wound around the pulley (5), one end of the rope is fixed to one end of the lever (3), the other end of the rope is fixed to the top of the pressure rod (6), the bottom end of the pressure rod (6) is fixed to the tray (8), and a weight (7) is placed on the tray (8).

6. The root soil shear strength double-sided shear tester according to claim 1, characterized in that, The telescopic mechanism includes: The telescopic rod is slidably engaged with the main frame (18), and one end of the telescopic rod is in contact with one side of the shear ring (11); The drive unit is in transmission cooperation with the telescopic rod.

7. The root soil shear strength double-sided shear tester and experimental method according to claim 6, characterized in that, The drive unit includes a stepper motor (1), the output shaft of the stepper motor (1) is connected to a worm gear, the worm gear meshes with a turbine, the turbine has a thread inside, the turbine is sleeved on the outside of the telescopic rod, and the telescopic rod is threadedly engaged with the turbine. The telescopic rod is provided with a sliding groove, and the main frame (18) is provided with a protrusion. The telescopic rod and the main frame (18) cooperate through the sliding groove and the protrusion to achieve axial sliding and radial limiting.

8. The root soil shear strength double-sided shear tester and experimental method according to claim 6, characterized in that: The sensor includes a load sensor (2) and a shear displacement sensor (19), which are located on both sides of the shear ring (11). One end of the load sensor (2) is fixed to the telescopic rod, and the other end of the load sensor (2) is in contact with the side wall of the shear ring (11); The fixed end of the shear displacement sensor (19) is fixedly connected to the main frame (18), and the movable end of the shear displacement sensor (19) is in contact with the side wall of the shear ring (11).

9. An experimental method for testing the shear strength of root soil under two-sided shear, using the root soil shear strength tester according to any one of claims 1-9, characterized in that, Includes the following steps: The sample obtained from in-situ culture of the target soil is placed in the cavity formed by the lower fixing ring (12), the shear ring (11) and the upper fixing ring (10); The reaction force unit provides a reaction force to one end of the sample; Pressure is applied to the other end of the sample via the pressurizing unit; The movable end of the telescopic mechanism extends out and pushes against one side of the shear ring (11) and moves it; Experimental data is acquired and processed using the sensor.

10. The experimental method for double-sided shear strength testing of root soil according to claim 9, characterized in that, The method for obtaining the sample through in-situ culture of the target soil includes the following steps: A standard cylindrical PVC pipe with a smooth inner wall is buried in the soil of the target site. The target plant is planted inside the PVC pipe; The target plant is allowed to grow naturally in the soil of the target site under in-situ stress, moisture and ecological environment for a predetermined period of time; After growth is complete, the PVC pipe, together with the complete root-soil composite formed inside the pipe, is excavated from the site as a whole sample and transported back to the laboratory.

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